While trenchless construction methods like directional drilling have received the majority of press over the last several years, one trenchless tool continues to prove its versatility, effectiveness and efficiency everyday—the pneumatic piercing tool. The piercing tool provides contractors, municipalities and utilities a tremendous amount of versatility as well. Contractors around the world continue to achieve high rates of production and efficiency with them.
SCE is a very environmentally conscious company. As part of their commitment to environmental protection, the electric power they provide for their customers includes more alternate and renewable energy (19%) from a greater variety of resources than nearly any other utility in the world. They have also been active in efforts to improve Southern California air quality since the 1940s. Their work with trenchless construction methods also speaks to the company’s environmental commitment.
SCE’s piercing tool project began with areas of cable-in-conduit (CIC) that needed to be replaced. SCE Technical Specialist Jim Wood said, “Several years ago, we started to have some failures from over heating with a couple areas of CIC. It was a situation that when the CIC was installed, there were only a few homes in the area. Now, the number of homes has grown substantially. We wondered what could be done and thought it would be great if we could somehow replace that conduit without having to tear up people’s yards, driveways and sidewalks. That’s how our move toward trenchless applications began.”
After discussions about the situation, Wood and other SCE colleagues traveled to an equipment tradeshow and connected with trenchless equipment manufacturer TT Technologies, Aurora, Ill. With TT Technologies’ years of trenchless equipment manufacturing experience, the two companies embarked on modifying existing technology to tackle the CIC replacement project.
TT Technologies piercing tool specialist Collins Orton said, “We needed to utilize a modified piercing tool application to replace the existing conduit. Working with SCE, we developed a specialized head that allowed us to use the piercing tool in a pipe bursting application.”
An Edison International (NYSE:EIX) company, Southern California Edison is one of the nation’s largest electric utilities, serving a population of more than 12 million via 4.6 million customer accounts in a 50,000-square-mile service area within central, coastal and Southern California. Southern California Edison is one of the largest electric utilities in the U.S., and the largest subsidiary of Edison International.
On an average day SCE provides power to over 12 million individuals, 430 cities and communities, 5,000 large businesses, 280,000 small businesses including 285,000 commercial, industrial, and non-profit customers in thriving areas of central, coastal and Southern California.
To deliver that power, it takes 16 utility interconnections, 4,990 transmission and distribution circuits, 425 transmission and distribution crews, the days and nights of more than 13,000 employees, and over a century of experience.
Keeping customers happy and making sure that power stays on are top priorities for SCE. Choosing a trenchless piercing tool for replacing the failing CIC would meet both of those goals.
Piercing Tool Versatility And Production
Because the piercing tool can be used in so many ways, it represents one of the most versatile construction tools available to a utility. With some creativity and applied knowledge, contractors and utilities can get an incredible amount of production from these simple tools.
While many water projects necessitate this standard horizontal boring application, other service installations require the piercing tool to transform into a pipe rammer in order to install a casing under a roadway that will house the new service line. Using a piercing tool as a pipe rammer is not a new idea. The pipe rammer is in many ways the direct descendent of the piercing tool.
For other projects, like the SCE project, the tool mutates again, used this time for pipe bursting. During pipe bursting an expander is attached to the piercing tool. The tool is guided through the existing pipe (host pipe) by a winch. As the tool travels through the pipe its percussive action breaks apart or splits the existing pipe or conduit. The expander, which is larger than the diameter of the existing pipe and typically larger than the diameter of the new pipe, forces the fragmented host pipe into the surrounding soil. The new pipe, often High Density Polyethylene (HDPE), is pulled in behind the tool simultaneously.
For SCE, the tool was fitted with a modified pipe bursting head that could be used with the small 1 1/4-inch diameter conduit that was already in the ground. The initial run was 280 feet. SCE crews began the project by excavating a small 4-foot by 4-foot launch pit at one end of the conduit to be replaced and a 4-foot by 4-foot exit pit at the other end. Then crews removed the existing cable while pulling in a poly rope. After the cable was removed, the crew attached the poly rope to the Grundowinch cable at the exit pit. The winch cable was then pulled back through the 1 1/4-inch conduit and attached to the modified piercing tool at the launch pit 280 feet away.
As the winch line was being installed, crews fused together the 280 feet of new 4-inch HDPE conduit. Once completed, the air hose for the tool was placed inside of the 4-inch HDPE and the new pipe string was connected to the 3-inch Grundomat and bursting was ready to start.
Bursting proceeded without incident, taking only 45 minutes to complete. Wood said, “In general everyone was impressed with the whole process and the way everything went. We have more CIC to replace and pipe bursting might come into play for future replacements.”
History Of The Piercing Tool
The first designs for the modern piercing tool date back to the early 1900s. The first patented designs incorporated all of the basic elements of today’s piercing tools. The piercing tool is basically a piston within a casing. Compressed air moves the piston and the impact of the piston drives the tool forward. That was the design of the first tool and it is essentially the same in principal today.
Early working models, however, were not developed until the 1950s and 1960s in Poland, Russia and Germany. The first tools, or moles as they are often referred to, were often difficult to handle and hard to restart after stopping. Accuracy was also a problem.
According to Orton, piercing tool technology was often thought of as unreliable and was not allowed to reach its full potential because accuracy was such a problem. The development of the reciprocating stepped-cone chisel-head assembly changed that in the 1970s.
Orton said, “The chisel-head assembly is spring-loaded and pushes forward from the main casing at a rate of approximately 9 times per second. This creates a pilot bore and helps the Grundomat maintain accuracy. The reciprocating action and stepped-cone design allow the tool to power through difficult soils and obstructions without being pushed off course.”
Today, piercing tools are used in water, gas, sewer, electrical, CATV and other construction applications. Typically piercing tools range in size from as small as 1 3/4 inches in diameter up to 7 inches. Accurate bores at lengths of 50 to 150 feet, make today’s piercing tools a far cry from their ancestors. In addition to horizontal boring, the tools can be used for other applications like pipe bursting and pipe ramming.
by Jim Schill
Utility Products Showcase, September 2005